Method and apparatus for gas plating nickel films with uniformity of resistance



Oct. 17, 1961 w. M. BOLTON ETAL 3,004,865

METHOD AND APPARATUS FOR GAS PLATING NICKEL FILMS WITH UNIFORMITY 0F RESISTANCE Filed Nov. 4. 1957 INVENTOR WI LBUR M. BOLTON RAYMOND L. RUSE V 0- BY 7% IWQM ATTORNEY United States Patent NIETHOD AND APPARATUS FOR GAS PLATING NICKEL FILMS WITH UNIFORMITY 0F RE- SISTANCE Wilbur M. Bolton, Piqua, and Raymond L. Ruse, Dayton,

Ohio, assignors, by mesne assignments, to Union Carbide Corporation, New York, N.Y., a corporation of New York Filed Nov. 4, 1957, Ser. No. 694,170 3 Claims. (Cl. 117107) This invention relates to the metallization of elongated substrates, and is particularly directed to the metallization' of rods, wires, yarns and similar structural configurations.

In the production of many electrical devices, such as otentiometers, for example, the uniformity of resistance per unit length is an extremely important factor. Such uniform resistance is dependent upon the uniformity of the metal which serves as the resistance element, both from the point of view of the chemical and physical characteristics of the metal. The plating of metals from a thermally decomposable metal bearing compound provides substantially pure metallic deposits from the chemical point of view.

The purpose of the present invention is to provide novel methods for the manufacture of elongated substrates with metal deposited from a heat decomposable compound, while providing in the deposited metal a uniformity of physical characteristics, particularly thickness of the deposit.

Yet another object of the invention is to provide novel apparatus for effecting uniform distribution of metal deposited from the gaseous state over an elongated substrate.

The invention will be more fully understood by reference to the following detailed description and accompanying drawings wherein:

FIGURE 1 is a perspective view of apparatus useful in the practice of the invention; and

FIGURE 2 is an enlarged sectional view illustrating a metallizing chamber adapted for use with the apparatus of FIGURE 1.

Referring now to the drawings more in detail, the numeral 1 in FIGURE 1 indicates a fragment of a table having suitable supporting legs such as illustrated at 3. Mounted on an extremity 5 of the table is a reversible electric motor 7. Also mounted on the right hand end of the table, as shown in FIGURE 1, are brackets 9, secured to a support 11 and mounting therebetween a drum 13. Drum 13 is rotatably supported on an extension of motor shaft 15 and a cable 17 passes over the drum. One end of the cable 17 is secured to a slide 19, while the other end of the cable passes over a pulley 21 at the left hand end of the table and is secured to the reverse side of slide 23 (FIGURE 1).

The table -1 mounts a plurality of supports 25; as shown in FIGURE 1 longitudinally extending tubular guide rods 27, 29 are mounted in the supports 25 and pass in parallel relation over the length of and above the table.

The slides 19, 23 are slidably mounted on the guide rods 27, 29. For this purpose bearings 31 of the slide 19 and bearings 33 of the slide 23 engage the rods 27, 29 to assist guiding of the slides on the rods and to provide a suitable bearing support for the slides. A rigid rod 35 extends between and is secured to the slides 19, 23 to retain the slides for movement together as a unit.

Rod 35 mounts a limit switch actuator 37 at the right hand end and a second limit switch actuator 39 at its left hand end. A limit switch 41 having a control switch 42 is mounted on beam section 43.

Referring now again to the slide 19, a bracket 44 secured to the slide mounts an electric motor 45, the shaft 3,004,866 Patented Oct. 17, 1961 ICC 47 of which carries a gear 49 meshing with a larger gear 51. Gear 51 has a pin 53 therethrough which supports a Jacobs chuck 55. As shown in FIGURE 1 the Jacobs chuck 55 receives an elongated substrate, such as a wire, 57. This wire may be wholly of metal, such as copper, or alternatively it may be copper coated with a film of resin, such as Formvar, a vinyl acetal resin. However, other enameled or resin wires or substrates may be employed.

Gear 49 has secured thereto rod 59 which is supported in bearing block61 mounted on the slide 19. This rod 59, at its remote extremity, passes through a bearing block 62 and carries on its remote end a small gear 63 which meshes with a larger gear 65. Gear 65, similar to gear 51, is provided with a pin (not shown) which supports a Jacobs chuck 67.

Accordingly operation of the motor 45 is effective, through the gear train, to rotate the wire 57, and rotation is occasioned at each slide in order to avoid twisting of the wire 57. Motor 45 is operated through a switch indicated at 68.

I The numeral 69 designates a support for a heater 71 over which the wire 57 is adapted to pass. Adjacent the heater 71 is a plating chamber 73 provided with a support 74. The plating chamber is discussed more particularly hereinafter in connection with FIGURE 2.

A conduit 75 leads into the upper end of the plating chamber 73 and this conduit is provided with a valve 77. A second conduit 79 leads out of the plating chamber to a coupling 80, which itself is provided with an exhaust 81, and an off-gas burner 83. The numeral designates a source of an inert gas, such as carbon dioxide, and a conduit 87 through valve 89 connects the inert gas source through the coupling 91 and conduit 92 with a mixing device 93. Mixing device 93 is supported in any suitable manner in a tank of hot water indicated at 94. Any heating arrangement or fluid useful as a bath may be utilized for this purpose.

Also supported in the water bath 94 is a source of heat decomposable metal bearing gas, such as nickel carbonyl, and which source is indicated at 95. The heat decomposable metal bearing gas is normally supplied to the source 95 from a supply cylinder (not shown). Cylinders containing nickel carbonyl under pressure are commercially available. Source 95 functions as a vaporizer and is connected through a conduit 96 having a valve 97 with a mixer 93. A conduit 98 leads from the mixer 93 to a flow meter 99, the outlet of which flow meter is connected to the conduit 75.

Referring now to the operation of the device, a wire or other substrate to be plated is supported as shown in FIGURE 1. The plating chamber 73 is first flushed of air by passing carbon dioxide through the chamber for a short period of time. This is accomplished by opening valve 89 and valve 77 while maintaining the valve 97 closed. When the chamber. has been thoroughly flushed of air, valve 97 is opened and nickel carbonyl from the source 95, gasified through the agency of the water bath, mixes with the carobu dioxide in the mixing device 93.

Suitably the temperature of the water bath is about 45 C. The flow rate of the nickel carbonyl is approximately 2 cc. per minute, and that of the carbon dioxide about 5 cc. per minute. Just prior to the time the gas is flowed to the plating chamber 73 the heater 71 is energized and the switch 43 thrown to the position shown in FIGURE 1 to render motor 7 operable. Suitably the wire is heated to 250 F. to 300 F. by heater 71. As the motor drives the slides 19, 23 in a leftwardly direction (FIGURE 1) the wire 57 is heated as it enters the plating chamber 73. A suitable temperature of this wire is about 300 F,

Also the motor 45 is energized to occasion rotation of the Wire as it moves rectilineally; this insures uniform deposition of nickel metal from the heat decomposable nickel carbonyl gas and the wire 57 is appropriately coated.

For heavy coatings the wire may be moved back and forth through the chamber since motor 7 reverses with successive contacts of the actuators 37, 39 with switch 41 when switch 42 is in the on position. In general, a heater 71 is suitably provided on each side of the chamber 73 for eiiecting this purpose, although such is not absolutely necessary where the substrate retains sufiicient heat to effect decomposition of the gas on the return stroke.

Other gaseous compounds than nickel carbonyl may be employed, for example, iron pentacarbonyl and chromium hexacarbonyl are'useful. Nickel carbonyl is particularly suitable as it decomposes readily to give a uniform film of uniform electrical resistance and is also available commercially in quantity. 7

As indicated more clearly in FIGURE 2 chamber 73 is adapted to seal against the wire 57 and to inhibit the escape of gases from the chamber. Chamber 73 is formed in two similar pipe section halves bolted together and having closing end plates as at 100, 101; retainer plates at 104 at each end are drawn against rubber discs '103 by bolt and nut combinations 105 to securely and resiliently compress the. discs against end plates 100, 101;-at each chamber end an aperture 106. is formed through the combination of end plate disc and retainer plate such that a wire 57 resiliently engages the discs as it passes through the chamber.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is: A

l. A process of metallizing elongated substrates which comprises the steps of supporting an elongated substrate for simultaneous rotational and longitudinal movement, rotating the substrate while simultaneously moving the substrate longitudinally through a housing defining a gas plating chamber, heating the substrate immediately prior to the passing of the substrate into the gas plating chamber and contacting the heated substrate with a thermally decomposable metal bearing gas which decomposes at the temperature of the heated substrate to deposit the metal of the gas on the substrate, circulating said thermally decomposable gas through the chamberas succeeding heated portions of the substrate traverse the chamber, and reversing the direction of longitudinal movement of the elongated substrate while continuing the rotational movement of the substrate to repeatedly present the substrate to the gas in the chamber whereby a uniform continuous coating of metal is deposited on said substrate. 7 V

2. Metallizing apparatus for gas plating metal on elongated elements comprising, in combination, a gas plating chamber having inletand outlet apertures through which an elongated element to be metallized may be passed, a longitudinal way arranged parallel to and spaced from each side of the plating chamber, a pair of parallel disposed slides arranged in opposed longitudinally spaced relation on opposite sides of the plating chamber and extending transversely between and supported by said ways, tie rod means connecting the slides together for rectilineal movement along the ways, means provided on each slide for retaining the elongated element being gas plated between said'slides for passage through said plating chamber, means for rotating said retaining means relative to said slides While said elongated element is moved lengthwise back-and-fourth through said gas platng chamber, means for driving said slides in rectilineal movement, means to limit the rectilineal movement of said slides in one direction of movement, and heater means disposed adjacent said inlet aperture of the'gas plating chamber for heating said elongated element immediately before entry of the same into said gas plating chamber.

3. Metallizing apparatus for gas plating metal on elongated elements comprising, in combination, a gas plating chamber having inlet and outlet apertures through which an elongated element to be metallized may be passed, a longitudinal way comprising a pair of guide rods arranged parallel to andspaced from each'side of said plating chamber, a pair of parallel disposed slides arranged in opposed longitudinally spaced relation on opposite sides of the plating chamber and extending transversely between and slidably, supported by said guide rods, tie rod means connecting saidslides together for rectilineal movement along said guide rods, means comprising a chuck provided on each slide for retaining the elongated element being gas plated between said slides for passage through said plating chamber, means for rotating said chuck means synchronously relative to said slides while said elongated element is simultaneously moved lengthwiseback-and-forth through said gas plating chamber, means comprising a motor for driving said slides in rectilineal movement, means to limit the rectilineal movement of said slides in one direction of movement, means for reversing the rectilineal movement for return movement of said. elongated element, and heater means disposed adjacent 'said inlet aperture of the gas plating chamber for heating said elongated element immediately before entry of the same into said gas plating chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,003,441 'Eaton Sept. 19, 1911 2,405,662 McManus et al. Aug. '13, 1946 2,638,423, Davis et al. May 12, 1953 2,656,283 Fink et al. Oct. 20, 1953 2,759,848- Sullivan Aug. 21, 1956 2,763,576 Belitz et al. Sept. d8, 1956 2,793,143 Kohring May 21, 1957 2,810,365 Keser Oct. 22, 1957 2,847,322 Drummond Aug. 12, 1958 2,853,970 Novak Sept. 30, 1958 2,859,130 Toulmin Nov. 4, 1958 2,867,552 Homer Jan. 6, 1959 

1. A PROCESS OF METALLIZING ELONGATED SUBSTRATES WHICH COMPRISES THE STEPS OF SUPPORTING AN ELONGATED SUBSTRATE FOR SIMULTANEOUS ROTATIONAL AND LONGITUDINAL MOVEMENT, ROTATING THE SUBSTRATE WHILE SIMULTANEOUSLY MOVING THE SUBSTRATE LONGITUDINALLY THROUGH A HOUSING DIFINING A PRIOR TO THE PASSING OF THE SUBSTRATE INTO THE GAS PLATING CHAMBER AND CONTACTING THE HEATED SUBSTRATE WITH A THERMALLY DECOMPOSABLE METAL BEARING GAS WHICH DECOMPOSES AT THE TEMPERATURE OF THE HEATED SUBSTRATE TO DEPOSIT THE METAL OF THE GAS ON THE SUBSTRATE, CIRCULATING SAID THERMALLY DECOMPOSABLE GAS THROUGH THE CHAMBER AS SUCCEEDING HEATED PORTIONS OF THE SUBSTRATE TRAVERSE THE CHAMBER, AND REVERSING THE DIRECTION OF LONGITUDINAL MOVEMENT OF THE ELONGATED SUBSTRATE WHILE CONTINUING THE ROTATIONAL MOVEMENT OF THE SUBSTRATE TO REPEATEDLY PRESENT THE SUBSTRATE TO THE GAS IN THE CHAMBER WHEREBY A UNIFORM CONTINUOUS COATING OF METAL IS DEPOSITED ON SAID SUBSTRATE. 